SYDNEY (AP) - Orica-GreenEDGE rider Daryl Impey of South Africa has been omitted from the team’s Tour de France lineup after failing a doping test.

Australian-based Orica-GreenEDGE released a statement Wednesday saying it was notified by The South African Institute for Drug-Free Sport that the 29-year-old delivered a positive A and B sample to the banned masking agent Probenecid after the South African Championships on February 6.

Impey became the first African rider to wear the Tour de France’s yellow jersey last year when he led the standings during stages six and seven. This year’s Tour starts Saturday in Leeds, England.

“Impey will not feature on the team’s roster until the case has been closed and he is fully eligible to ride,” Orica-GreenEDGE said.

Impey said in a statement he had no knowledge of Probenecid and had never knowingly taken the substance.

“I am committed to drug-free sport and fully intend to take all steps necessary to clear myself of any suspicion,” he said.

“I immediately flew back to South Africa and was present at the analysis of my B sample on 27 June 2014, the results of which confirmed the initial analysis.”